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Effect of perennial water on soil, vegetation and wild herbivore distribution in southeastern Zimbabwe.Clegg, Sarah. 19 December 2013 (has links)
The effects of artificially supplied perennial water on soil properties, vegetation dynamics and the
distribution of large herbivores was investigated in southeastern Zimbabwe. Data collection took
place between March 1997 and July 1998. Water points were situated primarily on three different
soil types (clay-loam, sandy-clay-loam and sand), and in four different vegetation types (Hill
communities, Colophospermum mopane veld, Acacia nigrescens woodland and Albizia petersiana
woodland). One water point in C. mopane veld (Bandama) had been closed two years prior to data
collection, while another, in the Hill community (Manyoka), had been introduced, two years prior to data collection.
Changes in physical (infiltration) and chemical (organic carbon and nutrients) properties of
soils around water points were largely restricted to within 100 m of water. Chemical enrichment of
the soil occurred only at water points that had been in place for more than two years. Soil surface
conditions were altered to distances beyond 100 m from water. Manyoka (the new water point) was
an exception, with extreme changes limited to within 100 m of water.
Herbaceous and woody species composition changed in response to distance from water
with changes best described by asymptotic equations. Changes in species composition of the woody
component appeared to be longer lasting than changes to the herbaceous component. Most perennial
grass species declined close to water, but Urochloa mosambicensis increased close to water in areas
outside of the Hills. Herbaceous species diversity was adversely affected by distance from water on
sandy soils (Hill communities and A. petersiana woodland), but was largely unaffected on clay-loam
(A. nigrescens woodland) and sandy-clay-loam soils (C. mopane veld). Woody species
composition and density was altered out to 500 m from perennial water in Acacia nigrescens
woodland on clay-loam soils. Results suggest that this vegetation type may be susceptible to bush
encroachment close to water. Trends in woody canopy utilisation were generally similar to trends in
woody species composition, and it is proposed that the former may be used to indicate future
changes in the latter. Conversion of trees to shrubs was highest at Manyoka (the new water point)
indicating that woody destruction by elephants is extreme during the initial years following water introduction.
Large herbivore biomass was greatest close to water (< 1 km) during the dry season but not
during the wet season. Herbivore species distributions appeared to be influenced by the position of
perennial water, but since all range was within easy access of water, it is unlikely that animal
distributions were constrained directly by the position of surface water. It is more likely that
herbivores were spatially separated on the basis of habitat type. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.
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An assessment of impacts of landfill composition on soil quality, heavy metal and plant health : a case of Lumberstewart landfill in Bulawayo, ZimbabweMakuleke, Peace 02 1900 (has links)
Landfills have served as the major sites for waste disposal in both developed and developing countries. Upon closure of a landfill site, the surface could be converted to a golf course, recreation park, playground, animal refuge, tennis court and industrial site. Even when closed, landfills still have the potential to contaminate the surrounding environment as a result of the migration of leachate from decomposing waste contained in the site. This study focused on assessing the
impacts of a closed landfill on soils and plants at Lumberstewart closed landfill site in Bulawayo, Zimbabwe. Soil samples were collected at three different depths (0-30 cm, 30 - 60 cm and 60-90 cm) at the landfill and a control site. The soil samples were analysed for their texture, pH, electrical conductivity, organic matter content, cation exchange capacity and concentrations of Cd, Cu, Cr, Fe, Ni and Zn. Samples of jimson weed and pigweed growing at the closed landfill and the control
site were collected from the same sites where soil samples were collected, and the concentrations of the same set of heavy metals in these weeds determined. Soil samples were digested using EPA
method 3050B: Acid Digestion of Sediments, Sludge and soils whereas nitric acid and hydrogen peroxide was used for digestion of plant samples. Both plant and soil digests were analyzed for heavy metals concentrations using Flame Atomic Absorption Spectrometry (AAS). Soils from the landfill as well as the control site had a high content of sand with soil pH values which were alkaline. The electrical conductivity values of the soil samples were relatively low ranging from 0.39 to 1.67 dS/m, indicating low levels of salts in soils at the landfill. The concentrations of heavy metals at the closed landfill site were higher than the control site. Heavy metals concentrations in soils at the closed landfill followed the order Fe>Zn>Cu>Cr>Ni>Cd. Results indicated that Fe was exceptionally higher than the other metals with concentration values averaging 45690±17255 mg/kg. Cadmium on the other hand had the least concentration with values of 0.01±0.00 mg/kg.
Values of Enrichment Factors of heavy metals around the soil at different depths indicated that the enrichment of heavy metals increased with depth at the landfill up to 30-60 cm after which a
decrease was observed. Values for heavy metal Contamination Factor of soils around the landfill ranged from low concentration (CF<1) to very high concentration (CF>6). The Pollution Load Index (PLI) values for the soil at the Lumberstewart landfill indicated that all sites were polluted (PLI>1). Site 6 had significantly higher mean concentration of heavy metals in soils at the landfill whereas site 11 had the least. The concentrations of Cd and Ni in soils at the landfill were below
permissible limits of South African National Norms and Standards (NNS) as prescribed by NEMA (2008) in South Africa whereas Cr, Cu and Zn in soils were above the NNS permissible limits.
Heavy metal concentrations in soils at the landfill were above World Health (WHO) permissible limits except for Cd which was equal (0.01 mg/kg) to the permissible values of Cd in the soils at sites 5, 8, 9, 10, 11 and 12. Mean concentrations of heavy metals in jimson weed and pigweed were in the order Fe>Zn>Cu>Cr>Ni>Cd. The concentrations of Cd, Cr, Cu, Fe and Zn in both plants from all sites at the landfill were significantly higher than the control site. Heavy metal transfer coefficient for both plants indicated that heavy metal uptake was more species dependent than soil heavy metal concentration dependent. The results from this research indicate that though the Lumberstewart Landfill has been closed, it is still affecting the soils in the vicinity of the
landfill. Plants and water around the Lumberstewart closed landfill could be at risk from heavy metal contamination. High concentrations of heavy metals observed in the soil could present a health risk to communities should they decide to use the landfill site for arable purposes. / Environmental Sciences / M. Sc. (Environmental Science)
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